1. Field of the Invention
This invention relates to a jig table apparatus for a machine tool.
2. Description of the Prior Art
Prior art jig table apparatuses have been proposed which include a pair of right and left jig tables, each being for holding thereon a work to be worked. The jig tables are mounted on a base member disposed cross-wise in front of a machine tool and are movable to the right and the left. The jig tables are so arranged that their alternate transferring to the right and left can be carried out by a transfer member which alternately selects a working station and a work attaching and detaching station, respectively. An elevating table is provided at the working station so that the selected jig table may be supported thereon so as to be movable downwards and a turntable is provided at the attaching and detaching station so that the selected jig table may be supported thereon so as to be turnable forwards and rearwards. Thus, the apparatus is operated such that the two jig tables are transferred to the right and the left such that alternately one of them is positioned in the working station and the other is positioned in the attaching and detaching station. The selected jig table positioned at the working station is then lowered to a ready-to-work position, while the selected jig table positioned at the attaching and detaching station is turned to the reverse side to a ready-toreplace position. In this case, it is required that the jig tables be brought into engagement with a transfer member for being transferred and are disengaged therefrom for lowering and turning. For effecting this changeover between engagement and disengagement, it has been usual hitherto that, in addition to respective first and second driving sources for the transfer member and the elevating table, it is necessary to provide a third driving source. Accordingly, in the above arrangement, the apparatus becomes complicated in construction and troublesome in operation.